Expand panel is not working .

Toan

I am creating a kendo panelbar that contains 3 panel and each panel contains kendogrid , the content will load data after kendodropdownlist change occur. If the first time I choose value on dropdownlist I can expand all panels, next time I choose another values on dropdownlist then I cannot expand panel anymore except the panel that set default expand: true and next time I can expand. I don't understand the reason why?

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